<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <script>
      // reduce(callbackFn, initialValue)
      //   callbackFn（previousValue，currentValue，currentIndex）:函数
      //   参数：previousValue：上一次调用 callbackFn 时的返回值
      //    currentValue：数组中正在处理的元素
      //   currentIndex：：数组中正在处理的元素的索引

      // 求和功能
      const array1 = [1, 2, 3, 4, 5]
      // 0 + 1 + 2 + 3 + 4
      const initialValue = 0
      const sumWithInitial = array1.reduce(
        (accumulator, currentValue) => accumulator + currentValue,
        initialValue
      )
      console.log(sumWithInitial)
    </script>
  </body>
</html>
